Question

It is known that a certain number of particles in a sample of water have enough kinetic energy to ‘escape’ from their intermolecular bonds and into the gas phase. But what is stopping these water vapour molecules from converting back into a liquid?

Answer 1

Water molecules evaporate from the liquid phase when they have sufficient kinetic energy. Condensation can convert water vapor back to liquid if the molecules lose energy. The balance between evaporation and condensation is influenced by temperature, energy, and pressure.

Step-by-step explanation:

Water molecules in liquid form evaporate when they have enough kinetic energy to overcome intermolecular forces. These energies are a result of the heat absorbed, allowing molecules, especially those at the surface, to escape into the gas phase.

Not all evaporated molecules remain in the gas phase; condensation can occur, turning gas back into a liquid. Condensation happens when the water vapor molecules lose energy and re-establish intermolecular bonds, essentially as a reverse process of evaporation.

This dynamic equilibrium between evaporation and condensation depends on temperature, energy within the system, and the surrounding pressure. In an open system, water vapor can disperse into the atmosphere, minimizing condensation. However, in a closed system, these molecules are likely to re-enter the liquid phase as they cannot escape into the environment.

When a liquid molecule has enough kinetic energy to escape into the gas state, it overcomes the intermolecular attractive forces in the liquid. However, in order for a water vapor molecule to convert back into a liquid, it needs to lose enough kinetic energy to be captured and pulled by the intermolecular forces.

This happens when the water vapor molecule comes in contact with a colder surface, such as a cooler object or a colder area of the air. When this happens, the water vapor condenses and returns to the liquid state.